In an LTE (Long Term Evolution) system, there are six standard system bandwidths in total: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, as shown in FIG. 1. A sequence such as an RS (Reference Signal) sequence or a scrambling code sequence is generated according to a maximum system bandwidth. For example, a sequence is generated according to a sequence length needed by 20 MHz. Then, a corresponding sequence is clipped out of the center of the sequence according to an actual system bandwidth, and the corresponding sequence is used as a sequence to be actually used. As shown in FIG. 2, mapping from a sequence to a frequency domain is performed by extending from a center frequency to two sides.
In an LTE system, a sequence is generated according to the following formula:
                    r                  1          ,                      n            ⁢                                                  ⁢            s                              ⁡              (        m        )              =                            1                      2                          ⁢                  (                      1            -                          2              ·                              c                ⁡                                  (                                      2                    ⁢                    m                                    )                                                              )                    +              j        ⁢                  1                      2                          ⁢                  (                      1            -                          2              ·                              c                ⁡                                  (                                                            2                      ⁢                      m                                        +                    1                                    )                                                              )                      ,          ⁢      m    =    0    ,  1  ,            …      ⁢                          ⁢      2      ⁢              N        RB                  max          ,                                          ⁢          DL                      -    1    ,where                ns is a timeslot number in a radio frame, 1 is a number of an OFDM (Orthogonal Frequency Division Multiplexing) symbol in a timeslot, c(i) is a pseudo-random sequence, and when a sequence is generated, an initialization status of a pseudo-random sequence generator may be used to distinguish sequences, for example:cinit=210·(7·(ns+1)+1+1)·(2·NIDcell+1)+2·NIDcell+NCP, where        NCP is one in a case of a normal CP (Cyclic Prefix), and NCP is zero in a case of an extended CP; and        c(2m) is generated according to the following formula:c(n)=(x1(n+Nc)+x2(n+Nc))mod 2x1(n+31)=(x1(n+3)+x1(n))mod 2x2(n+31)=(x2(n+3)+x2(n+2)+x2(n+1)+x2(n))mod 2, where        Nc is a constant.        
Sequences such as a scrambling code sequence and a pilot sequence are all generated in the manner of generating a pseudo-random sequence.
For the manner of generating a sequence according to a maximum system bandwidth and clipping a sequence, when the maximum system bandwidth is far greater than a bandwidth to be actually used, a sequence length to be actually used is far less than a sequence length that needs to be generated, which results in low sequence generation efficiency, wastes computing resources, and causes high energy consumption. This problem is more obvious when a system bandwidth exceeds 20 M.